Roots organic

if it's in a pot and you have fed to much and the plant is showing signs of toxicty, a little runoff will dilute the substrate. you do want to make sure you get the entire pot wet anytime you irrigate and that inevitably means a little runoff occurs. you can minimize it, since it just leeches off amendments in this context. if in the ground, you just have to water deeply enough. i have no idea what the generalized rules is for that. something you could google and find a reference for, though.

Is this outdoors or indoors? outdoors no, indoors also prob no, but maybe a bit of runoff once every month would not hurt. Typically if you using thins that need time to break down into the medium/soil like fish some compost teas its best not to water till runoff. It also is normally up to the microbes to manage the PH and not likely needed to PH down anything. Fish mix stuff tend to be of a lower PH in general and will act like a PH down product.